Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is the second image thereof;

FIG. 3 is the third image thereof;

FIG. 4 is the fourth image thereof; and,

FIG. 5 is the fifth image thereof.

The subject matter in this patent includes a process or period in which an image changes into another image. This process or period forms no part of the claimed design. The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-5.

The dashed broken lines showing portions of the display screen or portion thereof with graphical user interface are for environmental purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 